Filter element



T N A Y R w FILTER ELEMENT Filed April 26 INVENTOR.

fi/L r I 4 ATTORNEYS.

WITNESSES compact that it requires Patented July .2, 194

FELTIER William P. Yant, Pittsburgh, Pa,

ELEMENT assignor to Mine Safety Appliances Gompany, Pittsburgh,

Pa... a corporation of Application April 26,

3 Claims.

This invention relates to the purifying of air, and more particularly to a filter element especially suitable for respirators and the like.

It is among the objects of this invention to provide an air-filtering element which has a relatively large efi'ective area compared with its overall dimensions, which is extremely compact, and which is very inexpensive and simple in construction but dependable and effective in operation.

The preferred embodiment of the invention is illustrated in the accompanying drawing in which Fig. 1 is a section through an air-purifying unit; Fig. 2 is a plan view unit; and Fig. 3 is an enlarged fragmentary section of the filter element taken on line III- III' of Fig. 2.

Although this invention can be used wherever it is desirable to filter air, it is particularly applicable to canisters of the general type disclosed in United States Patent No. 2,019,928, granted to Charles W. Punton, and will therefore be described, by way of exemplification, with reference to such canisters; Those canisters generally comprise a casing provided withan outlet for purified air, and a cover provided with openings for the ingress of unpurified air. The cover and casing are formed in such amanner as to be adapted to clamp a sheet-likefilter element between them in the path of the air passing through the canister. ."i

In accordance with this invention, harmful constituents of gas or vapor, or particulate matter such as toxic dusts and other harmful solids and liquid mists, are removed from air to render it fit for breathing by an effective area materi practice in canisters of ally in excess of common the type just referred to, whereby to materially increase the capacity of the filter. When such a filter is used with a respirator, it allows sufficient air to pass through it for substantially unrestricted breathing, thus avoiding the discomfort and dangers of high breathing resistance. Likewise, the area of the filter element is so great that breathing resistance remains adequately low even though the pores in the element particulate matterfiltered out of the air passing through the filter. The filter element is so no largercanister than previously used with a fiat filter sheet.

Referring to Fig. 1 of the drawing, a casing l, which is preferably cylindrical, is provided with a circular base 2 and anupstandingside wall 3. The base is provided with an outlet opening adapted to be connected by a coupling 4 to the of the filter element of the i a filter element having become partly clogged by Pennsylvania i938, Senial No. 204L339 (ill. 133- 31) apparatus, such as breathing apparatus, which requires purified air. The open end of the. easing is normally closed by a removable cover It provided with a depending skirt l for receiving the side wall of the casing to which it is preferably threadably connected. The top of the cover is provided with a plurality of openings 8 for the admission of impure air. Disposed in the canister thus formed and in the path of all of the air passing therethrough is a filter element 9.

It is a feature of this invention that the effective area of my filter element is materially greater than the cross-sectional area of the inside of the canister so that the amount of air that can pass through the element per unit of time is greatly increased. Accordingly, the filter element is formed from a relatively large sheet of fibrous filter material which is folded to provide a series of reverse folds H. As shown in Fig. 3, the sheet is folded in such a manner that one layer 02 of each fold is narrower than the other layer l3 so that when the folds are disposed in overlapping relation they only partially overlap one another. Because of this, each fold adds to the width of the element instead of merely increasing the thickness of a stack of superimposed folds. The filter element may be conveniently formed to fit in the cylindrical canister described herein by folding a rectangular sheet of filter material in the manner just described, and then, with the folds lying substantially fiat in partially overlapping relation, cutting a circular portion out of the sheet, as shown in'Fig. 2. If the canister is of a shape other than circular, a filter element of a corresponding shape can be formed in the same manner.

The canister filter element thus formed is preferably held in the canister by clamping it therein around its edges. This may conveniently be done, as shown in Fig. 1,' by providing the upstanding wall 3 of the casing with an inwardly extending flange I6, and by providing the top of the cover witha downwardly projecting annular bead ll that overlies flange It. The edge of the filter element is tightly clamped between this bead and flange by screwing the cover tightly onto the casing so that leakage of impure air can not occur between the filter element and canister.

It is another feature of this invention that the overlapping layers of the folds of this filter element are prevented from engaging each other face to face and thereby decreasing the effective area of the element and increasing its thickimpure air-to enter between te'rial sheet whose pores are larger and more bulky ness. This is done by spacing means disposed between the fold layers, preferably by a plurality of substantially parallel narrow tapes l9 which, if flexible, may be secured to each side of the filter sheet before it is folded (Fig. 2). When the sheet is folded, these tapes become disposed between the layers of the folds, as shown in Fig. 3, and form spacing elements that hold the layers a slight distance apart to permit them and filter through substantially the entire surface area of the filter element. If the tapes are rigid or semi-rigid they may layers of the folded sheet either before or after it has been clamped in the canister.

While various sheet-like, filtering elements may be used, it is preferred to use a porous cellulosic material in sheet form and of such porosity as to satisfactorily remote particles of dust of the size encountered in use. That is, for coarse dusts there may be used a cellulosic macoarser than those of a paper used in a respirator for fine particles, such as those of smokes. Most suitably the filter element is formed from cellulose fiber sheet treated to provide pore openings of critical size. Such critical pore size is obtainable by impregnating the pores of foraminous material, suitably cellulosic sheets, with finely divided substances which clog the larger pores to provide a filter the pores of which will prevent passage of particles toube filtered out, i. e.. to provide critical pore size.

invention is relatively small and compact, but has an effective area equal to that of a much filter. Due to its small size it requires only a small and compact canister or the like to house it. The filter itself is not practiced otherwise be inserted between the.

. with a series of reverse folds, one

' A filter element made in accordance with this.

only simple and inexpensive, but an air-purifying unit inexpensively formed.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of theappended claims, the invention may be than as specifically illustrated and described.

I claim: I

1. A substantially flat air-purifying element comprising a sheet of filter material provided with a series of reverse folds, one layer of each fold being narrower than its other layer whereby said folds only partially overlap one another, and a thin reverse folded tape secured to said sheet and extending transversely of said folds to space them apart.

2. A. substantially fiat air-purifying element comprising a sheet of filter material provided with a series of reverse folds, one layer of each fold being narrower than its other layer whereby said folds only partially overlap one another, and a plurality of substantially parallel reverse folded tapes secured to said sheet and extending transversely of said folds to space them apart.

3. A substantially flat air-purifying element comprising a sheet of filter material provided layer of each fold being narrower than its other layer whereby said folds only partially overlap one another,

,said folds lying in close proximity to one another, the same manner as said and'a tape folded in sheet and mounted on each side thereof, the

tape folds being disposed between the sheet folds.

. WILLIAM P. YANT.

made with it may also be readily and 

